Showing papers on "Pyruvate kinase published in 1977"
TL;DR: Observations indicate that major changes in isozyme repertories do not necessarily accompany the thermoacclimatory responses of all fishes.
Abstract: Spectrophotometric and electrophoretic techniques were used to monitor qualitative and quantitative aspects of changes in 12 enzymes from five different tissues of green sunfish after thermal acclimation. Changes in dissolved oxygen concentrations over the range 5–25 ppm had no significant effect on qualitative or quantitative aspects of enzyme distributions.
In response to differences in environmental temperature, however, significant changes in the levels of activity of fructose-biphosphate aldolase, pyruvate kinase, lactate dehydrogenase, malate dehydrogenase, succinate dehydrogenase, cytochrome oxidase, cytochrome c, and glucose-6-phosphate dehydrogenase were observed in one or more tissues. Enzymes in a single metabolic pathway (e.g., glycolysis) usually exhibited parallel changes in a given tissue. Enzymes in different pathways, on the other hand, frequently exhibited changes in opposite directions, one group of enzymes increased in the cold while the other group decreased, indicating that major metabolic reorganizations were occurring. The patterns of change among tissues were distinctly different, therefore changes observed in one tissue cannot readily be generalized to other tissues.
No changes in isozyme patterns were seen for lactate dehydrogenase, creatine kinase, fructose-biphosphate aldolase, malate dehydrogenase, glucosephosphate isomerase, phosphoglucomutase, glycerol-3-phosphate dehydrogenase, or alcohol dehydrogenase in any of the tissues examined. However, some changes in the isozyme patterns of esterases in both liver and eye tissue were observed. These observations indicate that major changes in isozyme repertories do not necessarily accompany the thermoacclimatory responses of all fishes.
177 citations
TL;DR: The results suggest that the inability of trout to control blood glucose concentration is partly due to a lack of glucose-phosphorylating capacity.
Abstract: 1. The effects of diet composition and insulin treatment on blood glucose level, blood amino acid concentrations, the activities of two hepatic gluconeogenic enzymes (fructose diphosphatase, EC 3.1.3.11; phosphoenolpyruvate carboxykinase, EC 4.1.1.32) and of two hepatic glycolytic enzymes (hexokinase, EC 2.7.1.1; pyruvate kinase, EC 2.7.1.40) were examined in rainbow trout (Salmo gairdneri).2. Blood glucose levels were much higher in trout given a high-carbohydrate (HC) diet than in those given a high-protein (HP) diet. Insulin reduced blood glucose concentration in the HC-fed fish but had no effect in HP-fed fish.3. Plasma amino acid concentrations were higher in HP-fed trout than in HC-fed trout. Insulin reduced plasma amino acid levels in both groups.4. Gluconeogenic enzyme activities were higher in HP-fed trout than in HC-fed trout. Insulin reduced phosphoenolpyruvate carboxykinase activity in HP-fed trout but had no effect on either enzyme activity in the HC-fed trout.5. Pyruvate kinase activity was greater in HC-fed trout than in HP-fed trout. Insulin did not affect pyruvate kinase activity in the HC-fed trout but reduced it in HP-fed trout.6. Hexokinase activity was not affected by the diet treatments used, but was enhanced in the trout treated with insulin. Glucokinase (EC 2.7.1.2) was not detected in any of the trout livers.7. The results suggest that the inability of trout to control blood glucose concentration is partly due to a lack of glucose-phosphorylating capacity. Gluconeogenesis is controlled in response to diet and insulin by changes in enzyme level and by variation in concentration of gluconeogenic substrates.
174 citations
Journal Article•
TL;DR: Emphasis is placed upon the apparent derepression of the fetal isozyme in hepatomas and the influence of neoplasms and their extracts on the expression of pyruvate kinase in the liver of host animals.
Abstract: The relationships among and the properties of the pyruvate kinase isozymes are reviewed, emphasizing their potential role in carcinogenesis. Particular consideration is given to evaluation of the concept that the three major nonreadily interconvertible forms are the products of distinct genes, the relationship of these forms to additional separable forms of pyruvate kinase, the types and possible functions of interconvertible forms of the major isozymes, and mechanisms affecting the genetic expression of the isozymes. Emphasis is placed upon the apparent derepression of the fetal isozyme in hepatomas and the influence of neoplasms and their extracts on the expression of pyruvate kinase in the liver of host animals.
139 citations
TL;DR: The reaction of 5'-p-fluorosulfonylbenzoyladenosine with pyruvate kinase exhibits several of the characteristics of affinity labeling of the enzyme, consistent with the postulate that lysyl or tyrosyl residues are the most probably candidates for the critical amino acids.
Abstract: Rabbit muscle pyruvate kinase is irreversibly inactivated upon incubation with the adenine nucleotide analogue, 5'-p-fluorosulfonylbenzoyladenosine. A plot of the time dependence of the logarithm of the enzymatic activity at a given time divided by the initial enzymatic activity(logE/Eo) reveals a biphasic rate of inactivation, which is consistent with a rapid reaction to form partially active enzyme having 54% of the original activity, followed by a slower reaction to yield totally inert enzyme. In addition to the pyruvate kinase activity of the enzyme, modification with 5'-p-fluorosulfonylbenzoyladenosine also disrupts its ability to catalyze the decarboxylation of oxaloacetate and the ATP-dependent enolization of pyruvate. In correspondence with the time dependence of inactivation, the rate of incorporation of 5'-p-[14C]fluorosulfonylbenzoyladenosine is also biphasic. Two moles of reagent per mole of enzyme subunit are bound when the enzyme is completely inactive. The pseudo-first-order rate constant for the rapid rate is linearly dependent on reagent concentration, whereas the constant for the slow rate exhibits saturation kinetics, suggesting that the reagent binds reversibly to the second site prior to modification. The adenosine moiety is essential for the effectiveness of 5'-p-fluorosulfonylbenzoyladenosine, since p-fluorosulfonylbenzoic acid does not inactivate pyruvate kinase at a significant rate. Thus, the reaction of 5'-p-fluorosulfonylbenzoyladenosine with pyruvate kinase exhibits several of the characteristics of affinity labeling of the enzyme. Protection against inactivation by 5'-p-fluorosulfonylbenzoyladenosine is provided by the addition to the incubation mixture of phosphoenolpyruvate. Mg-ADP or Mg2+. In contrast, the addition of pyruvate, Mg-ATP, or ADP and ATP alone has no effect on the rate of inactivation. These observations are consistent with the postulate that the 5'-p-fluorosulfonylbenzoyladenosine specifically labels amino acid residues in the binding region of Mg2+ and the phosphoryl group of phosphoenolpyruvate which is transferred during the catalytic reaction. The rate of inactivation increases with increasing pH, and k1 depends on the unprotonated form of an amino acid residue with pK = 8.5. On the basis of the pH dependence of the reaction of pyruvate kinase with 5'-p-fluorosulfonylbenzoyladenosine and the elimination of cysteine residues as possible sites of reaction, it is postulated that lysyl or tyrosyl residues are the most probably candidates for the critical amino acids.
127 citations
TL;DR: It is suggested that the capacity of starved cells to maintain high intracellular concentrations of PEP and 2-PG is a consequence of decreased in vivo activity of this key regulatory enzyme of glycolysis.
Abstract: In the absence of an exogenous energy source, galactose-grown cells of Streptococcus lactis ML3 rapidly accumulated thiomethyl-beta-D-galactopyranoside (TMG) and 2-deoxyglucose to intracellular concentrations of 40 to 50 mM. Starved cells maintained the capacity for TMG uptake for many hours, and accumulation of the beta-galactoside was insensitive to proton-conducting ionophores (tetrachlorosalicylanilide and carbonylcyanide-m-chlorophenyl hydrazone) and sulfydryl group reagents including iodoacetate and N-ethylmaleimide. Fluorimetric analysis of glycolytic intermediates in extracts prepared from starved cells revealed (a) high intracellular levels of phosphoenolpyruvate (13 mM; PEP) and 2-phosphoglycerate (approximately 39 mM; 2-PG), but an absence of other metabolites including glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-diphosphate, and triosephosphates. The following criteria showed PEP (and 2-PG) to be the endogenous energy source for TMG accumulation by the phosphotransferase system: the intracellular concentrations of PEP and 2-PG decreased with concomitant uptake of TMG, and a close correlation was observed between maximum accumulation of the beta-galactoside and the total available concentration of the two intermediates; TMG accumulated as an anionic derivative, which after extraction and incubation with alkaline phosphatase (EC 3.1.3.1) formed the original analogue; fluoride inhibition of 2-phospho-D-glycerate hydrolyase (EC 4.2.1.11) prevented the conversion of 2-PG to PEP, and uptake of TMG by the starved cells was reduced by 80%; and the stoichiometric ratio [TMG] accumulated/[PEP] consumed was almost unity (0.93). In cells metabolizing glucose, all intermediates listed in (a) and (b) were found. Upon exhaustion of glucose from the medium, the metabolites in (b) were not longer detectable, while the intracellular concentrations of PEP and 2-PG increased to the levels previously observed in starved cells. The glycolytic intermediates in (b) are all in vitro heterotropic effectors of pyruvate kinase (adenosine 5'-triphosphate:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) from S. lactis ML3. It is suggested that the capacity of starved cells to maintain high intracellular concentrations of PEP and 2-PG is a consequence of decreased in vivo activity of this key regulatory enzyme of glycolysis.
118 citations
TL;DR: Comparisons of several enzymes of energy metabolism in AM and PM indicate that one basis for the differences in cell energetics is a difference in activity of key enzymes of both the oxidative phosphorlyative and the glycolytic sequences, suggesting that molecular O2 modifies the intrinsic cellular regulation of some enzymes ofenergy metabolism.
Abstract: Alveolar macrophages (AM) and peritoneal macrophages (PM) originate from common precursor cells, but function in different O2 environments. In the present studies, the impact of different O2 tensions on cell metabolism has been quantitatively determined, an enzymatic basis for these differences established, and a mechanism which regulates enzymatic differences demonstrated. O2 consumption and lactate production were compared in rabbit AM and PM in air and nitrogen. In air, AM demonstrate significantly greater O2 utilization. In nitrogen, (where glycolysis is the major source of energy provision) lactate production is two- to threefold greater in the PM. A comparison of several enzymes of energy metabolism in AM and PM indicate that one basis for the differences in cell energetics is a difference in activity of key enzymes of both the oxidative phosphorlyative and the glycolytic sequences. Exposure of cultivated AM to hypoxic conditions results in changes in the activity of these enzymes such that the AM closely resembles the PM. A key enzyme in oxidative phosphorylation (cytochrome oxidase) shows decreased activity and reaches values similar to those found in the PM. A key enzyme in glycolysis (pyruvate kinase) shows increased activity to values resembling those found in the PM. These alterations in enzyme pattern occur in isolated cell systems, suggesting that molecular O2 modifies the intrinsic cellular regulation of some enzymes of energy metabolism. Alterations in O2 tension may lead to alterations of the rate of biosynthesis and (or) the rate of biodegradation of key enzymes involved in oxidative phosphorylation and glycolysis. In turn, the alteration of enzyme patterns leads to a more suitable bioenergetic pattern as a function of O2 availability.
103 citations
TL;DR: Changes in levels of labeled compounds led us to conclude that pyruvate kinase was activated by ammonia, resulting in increased transfer of photosynthetically incorporated carbon to synthesis of amino acid skeletons at the expense of sucrose synthesis.
Abstract: Alfalfa (Medicago sativa L., var. El Unico) leaf discs, floating on buffer containing NH4Cl and photosynthesizing with 14CO2, produced more labeled amino acid and less sucrose than did control discs (no added NH4Cl). The level of pyruvate increased and that of phosphoenolpyruvate decreased. These and other changes in levels of labeled compounds led us to conclude that pyruvate kinase was activated by ammonia, resulting in increased transfer of photosynthetically incorporated carbon to synthesis of amino acid skeletons at the expense of sucrose synthesis. Carbon flow through enzymes catalyzing the anaplerotic reactions was apparently stimulated.
90 citations
TL;DR: The results are in accord with the view that the effects of glucagon and epinephrine on gluconeogenesis are not identical, with the effect being about 3 times greater in liver cells from fed rats than in those from fasted rats.
82 citations
TL;DR: The concentration of phosphoenolpyruvate was higher than normal in the livers of anesthetized rats in conditions like fasting and diabetes in which the rate of gluconeogenesis is known to be higher and the activity of pyruVate kinase lower than normally.
Abstract: The cyclic-AMP-dependent inactivation of pyruvate kinase L has been studied in a crude Sephadex filtrate of isolated hepatocytes. This inactivation requires the presence of Mg-ATP (apparent Km= 0.1 mM) and a half-maximal rate of inactivation was obtained in the presence of 0.15 μM cyclic AMP. It was inhibited by physiological concentrations of phosphoenolpyruvate and by micromolar concentrations of fructose bisphosphate and these inhibitory effects were counteracted by Mg-ATP and by several l-form amino acids such as cysteine, alanine, serine, phenylalanine, which are also ligands of pyruvate kinase. As a rule, it appears that effectors that increase the activity of the enzyme are also those which prevent its cyclic-AMP-dependent inactivation and vice-versa.
Considering the potentially important role of phosphoenolpyruvate concentration in the control of gluconeogenesis, experiments were performed to check if the inhibitory action of this metabolite on the inactivation of pyruvate kinase was of importance in vivo. We found that the concentration of phosphoenolpyruvate was higher than normal in the livers of anesthetized rats in conditions like fasting and diabetes in which the rate of gluconeogenesis is known to be higher and the activity of pyruvate kinase lower than normally. The reverse was true upon sucrose feeding. Inactivation of pyruvate kinase was induced in vivo by the administration of glucagon. This inactivation was less important in the livers with high concentrations of phosphoenolpyruvate and vice-versa. It is proposed that phosphoenolpyruvate exerts an important buffering effect in the variations of the rate of gluconeogenesis.
68 citations
61 citations
TL;DR: The activities of some glycolytic and associated enzymes have been determined in the muscles of trout and carp to investigate the possibility that the discrepancies previously reported between lactate accumulation and anoxic tolerance in these two fish result from underlying differences in gly colytic potential.
Abstract: The activities of some glycolytic and associated enzymes have been determined in the muscles of trout and carp to investigate the possibility that the discrepancies previously reported between lactate accumulation and anoxic tolerance in these two fish result from underlying differences in glycolytic potential. Steady state concentrations of certain glycolytic intermediates were also determined in freeze-clamped muscles from tankrested fish. The activities of hexokinase, phosphorylase and phosphofructokinase were approximately 2–3 times lower in carp than trout white muscles. Pyruvate kinase and lactate dehydrogenase activities were 5 times lower in carp white muscle. The lower, broader pH optima of lactate dehydrogenase and pyruvate kinase from carp compared to trout muscles is thought to be correlated with the greater anoxic tolerance of the carp. Glycolytic enzyme profiles were markedly different between the red and white muscles of the rainbow trout but broadly similar, with the exception of hexokinase activity, for the corresponding muscles of the carp. The results are discussed in relation to what is known about anaerobiosis in these two species and the comparative physiology of red and white muscles in fish.
TL;DR: The most likely hypothesis is that both these enzymes are coded by the same single gene, the slight electrophoretic differences between them being due to post-synthetic tissue-specific changes.
TL;DR: The inhibitory effects of C18:2 or Ci8;3 appear not to be mediated through changes in total plasma free fatty acid levels, in total hepatic long chain acyl CoA concentration or in hepatic cytosolic redox state.
Abstract: Rats were trained to eat a fat-free high carbohydrate diet from 800 to 1100 hours each day. After adaptation to meal-eating, the fat- free diet was supplemented with 8% methyl stA©arate(Ci8;o) or 3% methyl linoleate (Ci8:2) for 7 days. Relative to the fat-free group, hepatic utiliza tion of acetate unit equivalents (C2 units) for fatty acid synthesis per mg soluble protein by the Ci8:o group was not significantly altered, whereas Ci8:2 supplementation significantly depressed hepatic fatty acid synthesis. Supplemental Ci8:2 also caused a significant decline in liver fatty acid synthetase and acetyl CoA carboxylase while fat-free and Ci8:o groups dis played similar enzyme activities. Within a treatment, C2 unit utilization tor in vivo fatty acid synthesis was identical to that of acetyl CoA car boxylase and fatty acid synthetase activities in vitro. Therefore, shortly after a meal, the hepatic activities of these two enzymes appear to be functioning at near capacity. Ci8:2 supplementation to the fat-free diet for 7 days caused a 25% decline in glucokinase and pyruvate kinase activ ities, but only pyruvate kinase was significantly depressed. In contrast, citrate cleavage enzyme and fatty acid synthetase were both significantly reduced in activity by 50%. Plasma unesterified fatty acid levels in rats fed Ci8:2 for 5 days were not significantly elevated prior to a meal, al though dietary Ci8:2 did cause a fourfold rise in plasma free linoleate. Quantitation of long chain acyl CoA esters in freeze-clamped liver tissue of rats fed fat-free or fat-free plus 3% Ci8:2 or Ci8:3 diets revealed no con centration differences between treatments either before or after a meal. Similarly, lactate and pyruvate concentrations as well as the lactate: pyru vate ratios were not significantly changed by dietary Ci8:2 or Ci8:3. The inhibitory effects of C18:2 or Ci8;3 appear not to be mediated through changes in total plasma free fatty acid levels, in total hepatic long chain acyl CoA concentration or in hepatic cytosolic redox state. J. Nutr. 107: 1277-1287, 1977.
TL;DR: The conformations adopted by pyruvate kinase in the presence of allosteric inhibitors make it a better substrate for the protein kinase, compared with mixed histone or a synthetic heptapeptide.
TL;DR: At least one function of the phosphoprotein phosphatase may be to remove phosphate groups from the phosphorylated form of pyruvate kinase in the liver.
TL;DR: It is concluded that pyruvate kinase is phosphorylated in the intact liver cell in 32P-labelled slices from rat liver.
TL;DR: Yeast strains carrying recessive mutations representing four different loci that cause defects in pyruvate kinase, pyruVate decarboxylase, 3-phosphoglycerate Kinase, and 3- phosphoglycerates mutase were isolated and partially characterized.
Abstract: Yeast strains carrying recessive mutations representing four different loci that cause defects in pyruvate kinase, pyruvate decarboxylase, 3-phosphoglycerate kinase, and 3-phosphoglycerate mutase were isolated and partially characterized Cells carrying these mutations were unable to use glucose as a carbon source as measured in turbidimetric growth experiments Tetrad analysis indicated that these mutations were not linked to each other; one of the mutations, that affecting phosphoglycerate kinase, was located on chromosome III
TL;DR: These studies suggest that the myocardial creatine kinase system promotes rapid equilibration of CPK substrates throughout the cytoplasmic compartment while fluctuations of ATP and ADP are minimized while CP/creatine ratios and P 1 communicate energy demands of the contractile system to the mitochondria.
TL;DR: The levels of each of the glycolytic enzymes were observed to exhibit a parallel increase of 200 to 300% when human lymphocytes were stimulated to undergo blast transformation, which resulted in electrophoretic artifacts with lower pI values.
TL;DR: The purpose of this work was to study the nature of those two molecular forms of the erythrocyte enzyme in relation to the L-type enzyme from liver.
TL;DR: An examination of the regulatory properties of the individual enzymes after partial purification offers support for the hypothesis that an intricate regulatory system is required to permit a proper flow of metabolites through the pathways and to prevent futile cycling.
TL;DR: The results indicate that at all the above stages of club development the reactions catalysed by phosphoglucomutase, glucosephosphate isomerase, phosphoglycerate mutase and enolase were close to equilibrium, but those catalysedBy phosphofructo-kinase and pyruvate kinase were considerably displaced from equilibrium.
TL;DR: When carbon supply and energy production were dissociated by supplying the mutant strain with dextrose, adenine nucleotide levels fell dramatically, suggesting that the initial reactions of glycolysis are not rate limiting, nor are they readily inhibited by feedback controls.
Abstract: A mutant of the yeast Saccharomyces cerevisiae that is deficient in pyruvate kinase activity has been isolated. The mutant strain is capable of growth when supplied with lactate as the carbon source but not capable of growth when supplied with dextrose or other fermentable sugars or glycerol as the carbon source. Genetic analysis demonstrated that the phenotype of the pyruvate kinase-deficient strain was due to a single nuclear mutation, which was designated pyk1, and preliminary genetic mapping experiments located the pyk1 locus on chromosome I, 30 centimorgans from the ade1 locus. Adenine nucleotide levels in the mutant and parental strains were compared when the cells were subjected to various growth and starvation conditions. When carbon supply and energy production were dissociated by supplying the mutant strain with dextrose, adenine nucleotide levels fell dramatically. This result suggests that the initial reactions of glycolysis are not rate limiting, nor are they readily inhibited by feedback controls.
TL;DR: Synthetic polypeptides were employed as substrates in kinetic analyses of the reaction mechanism for the catalytic subunit of a cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) from calf thymus, consistent with a sequential reaction mechanism involving a ternary complex between enzyme,polypeptide substrate, and ATP.
Abstract: Synthetic polypeptides were employed as substrates in kinetic analyses of the reaction mechanism for the catalytic subunit of a cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) from calf thymus. This enzyme preparation was shown to catalyze the transfer of phosphate from ATP to histone H1 from calf thymus, as well as to two synthetic polypeptides, Arg-Lys-Ala-Ser-Gly-Pro (H1-6) and Arg-Arg-Lys-Ala-Ser-Gly-Pro (H1-7), corresponding to the amino acid sequence about serine-38 in calf H1. A related, basic heptapeptide corresponding to a sequence from pig liver pyruvate kinase, Leu-Arg-Arg-Ala-Ser-Leu-Gly (K), was also a substrate. The stoichiometry of peptide phosphorylation was established in each case as the transfer of 1 mol of phosphate from the γ position of MgATP to the serine hydroxyl of 1 mol of the peptide. Steady-state, initial-velocity, kinetic parameters were determined for each substrate, using various concentrations of ATP. Under the conditions used, all synthetic peptides reacted with greater maximum velocities than whole histone H1. Nevertheless, the Km for H1, 54 μM, was lower than the Km values of the synthetic substrates. The most efficient substrate was peptide K, which had a Vmax of 50.6 μmol/min per mg of kinase and a Km of 63 μM. In the absence of peptide substrate no ATPase activity was detectable at a sensitivity of 0.05% of the rate of peptide phosphorylation, suggesting that ATP is not cleaved to form an unstable phosphoenzyme complex. The data are consistent with a sequential reaction mechanism involving a ternary complex between enzyme, polypeptide substrate, and ATP.
TL;DR: The results implicate the poise of the HCO3-:CO2 system as a major determiner of endproduct accumulation in H. diminuta.
Abstract: The properties of pyruvate kinase (PK) and phosphoenol pyruvate carboxykinase (PEP CK), two enzymes that determine the preferrential accumulation of either succinate or lactate as endproducts of carbohydrate metabolism, are described in adult Hymenolepis diminuta. PK activity at Vmax and Km levels of PEP was unaffected by ATP, alanine, FDP4, or H+ ions, but was inhibited by 50% at 6.3 mM L-lactate and 30 mM HCO3−. The addition of 30 mM HCO3− increased the Km (PEP) by 6-fold but did not alter the Vmax. The inhibition of PK by HCO3− cannot be explained entirely by an effect of ionic strength, but probably represents a specific modulator-enzyme interaction. Under similar conditions PEP CK was maximally activated. Although L-lactate inhibited PEP CK (Ki(lac) = 1.8 mM), this effector may play a minor role in regulation of PEP flux. These results implicate the poise of the HCO3− :CO2 system as a major determiner of endproduct accumulation in H. diminuta.
TL;DR: The present work demonstrates the applicability of the molecular correlation concept and much of the altered biochemical pattern discovered in the rat hepatoma spectrum to other tumors in rat, to lymphomas in mice and to primary kidney tumor in humans.
TL;DR: It is concluded that, contrary to a previous report, avian liver contains pyruvate kinases type M2 and L as the mammalian liver does.
Abstract: A procedure for the simultaneous purification of both isoenzymes of pyruvate kinase (type M2 and L) from chicken liver has been worked out. Each isoenzyme produces a single band in dodecylsulfate gel electrophoresis. Each has a molecular weight of 190 000 and contains four apparently identical subunits of Mr = 50 000. The isoenzymes differ in their isoelectric points (type L: 6.3; type M2: 8.3) and their kinetic behaviour. Pyruvate kinase type L had an S-shaped phosphoenolpyruvate saturation curve (K 0.5=0.79 mM) which was transformed into an hyperbola in the presence of fructose 1,6-bisphosphate, while type M2 had a phosphoenolpyruvate saturation curve of the Michaelis-Menten type (K0.5=0.2mM). Antibodies against pyruvate kinase type L from chicken liver inactivated type L from rat and partially inactivated type M2 from chicken and rat; but the antibodies against type L did not react with type M1 from chicken breast muscle. It is therefore concluded that, contrary to a previous report (Strandholm, J.J. et al. (1975) Biochemistry 14, 2242-2246), avian liver contains pyruvate kinases type M2 and L as the mammalian liver does.
TL;DR: A cAMP-independent protein kinase from chicken liver phosphorylated and inactivated pyruvate kinase type M2 from the same tissue and the differences between the properties of thisprotein kinase in the interconversion of pyruVate Kinase and that described previously are discussed.
Abstract: A cAMP-independent protein kinase from chicken liver phosphorylated and inactivated pyruvate kinase type M2 from the same tissue. Complete inactivation was reached when 4 mol of phosphate were incorporated/mol of tetrameric pyruvate kinase. The protein kinase bound with high affinity to pyruvate kinase type M2 (Km value for pyruvate kinase = 6 X 10(-10)M; it phosphorylated phosvitin and casein but not histones, ATP and GTP were substrates. The differences between the properties of this protein kinase in the interconversion of pyruvate kinase and that described previously are discussed.
TL;DR: The data indicate that the energy generating system of the cells is most active in the lag phase, and major increases in the level of NADPH and ATP and energy charge were observed in the initial or lag period of culture.
Abstract: Measurements were made of the levels of key glycolytic intermediates and co-factors during the growth of Acer pseudoplatanus L. cells in batch culture. Mass action ratios were calculated for the enzymes phosphoglucoseisomerase, phosphofructokinase and pyruvate kinase. The ratio for phosphofructokinase was greatly displaced from equilibrium.
Major increases in the level of NADPH and ATP and energy charge were observed in the initial or lag period of culture. The data indicate that the energy generating system of the cells is most active in the lag phase.